The monoclonal antibody Ki-67, prepared by our group,3 reacts with a nuclear antigen present in proliferating cells but absent in quiescent cells. A detailed cell cycle analysis showed that the Ki-67 antigen is expressed throughout the whole cell cycle, making the antibody suitable for the determination of the growth fraction of a benign or malignant human cell subset.4 We recently showed a highly significant correlation between the proportion of Ki-67 positive cells and the histological classification of malignant nonHodgkin's lymphomas into high and low grade malignancies.5 Thus the determination of the growth Accepted for publication 9 April 1986 fraction with Ki-67 might be a new and reliable prognostic marker for these tumours.The evaluation of cell kinetic data in mammary carcinomas should also be undertaken for tumour grading, as this can provide reproducible prognostic information.This paper reports on the immunohistological determination of the growth fraction with Ki-67 in a variety of breast tumours and compares the results with conventional histological grading. Material and methodsThirty benign mammary lesions and 160 mammary carcinomas from patients attending the gynaecology clinics at the Klinikum Steglitz, and the Medical School, Hannover, were studied. There were 148 invasive ductal carcinomas, nine invasive lobular carcinomas, three medullary carcinomas and no carcinomata in situ. Cryostat sections of biopsy specimens were immunostained with monoclonal antibody

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Having observed that with iPath we have succeeded in satisfying all our telepathology needs, we are inclined to put the emphasis on the nature of the tasks being performed, as opposed to the methods or technical means for performing a given task. The three organisation models proposed by Weinstein et al. (2001) can be reduced to only two models: the model of discussion groups and the model of expert groups (virtual institutes).

The monoclonal antibody Ki-67 reacts with a human nuclear associated with cell proliferation that is expressed only in the G1, S, G2, and M phases of continuously cycling cells. This offers a simple opportunity to determine the growth fraction of tumors by immunostaining of fresh tissue. One hundred fifty-four invasive carcinomas of the breast were used in this study. The average number of Ki-67 positive cells was 15.3 +/- 10.1% (range, 1%-48%), whereas in 41 benign lesions of the breast only 4.4 +/- 2.6% (range, 1%-10%) of cells were positive. A correlation was found between growth fractions and histologic grading. On average, N+ tumors with less than four positive lymph nodes had a significantly higher growth fraction (20.4 +/- 14.2%) than N0 tumors (13.0 +/- 9.2%), whereas N+ tumors with more than three lymph node metastases had only 17.3 +/- 3.6% Ki-67 positive cells. This method yielded similar results to those obtained by other researchers through the use of flow cytometry and thymidine labeling. Determination of growth fractions by Ki-67 is suitable for routine use and may be useful in prognosis and in the selection of patients for various treatment modalities.